Shot in the dark: try booting in Safe Mode and see if the freezing still occurs. That will purge the font caches at the same time. Last time I had such problems, it was down to fonts.

iMac (19,1, 3.1 GHz i5, 12.7.4, 40 Gb RAM); MacBook Air (1.8 Ghz, 8 Gb RAM, 10.14.6, 256 Gb SSD) Vodafone router and Devolo Wi-Fi Extender, Canon TS8351 printer/scanner.